Packagers, to ensure adequate sterilization, often fill bottles and containers with liquids or products at an elevated temperature of approximately 180° F. to 205° F. (82° C. to 96° C.) and seal with a closure before cooling. Manufacturers generally refer to this as a “hot-fill” container or as a “hot-filling” process. As the sealed container cools, a slight vacuum, or negative pressure, forms inside causing the container to slightly change shape, particularly when made of polymer materials and generally having a somewhat flexible nature.
Typically, although not always, manufacturers produce these hot-fill containers in polyester materials, such as polyethylene terephthalate (PET), using a “stretch blow-molding” process, well known in the art, that substantially biaxially orients material molecular structure within the container. While PET materials are typical, other polymer materials, such as polypropylene, polyethylene, polycarbonate, and other polyesters, such as polyethylene naphthalate, are feasible using a variety of container production processes, also well known in the art, which may or may not establish the biaxial oriented material molecular structure.
Container and bottle designers attempting to control the change-in-shape from hot-fill often incorporate a plurality of generally recessed vacuum panels within the sidewalls around the container's body. Those skilled in the art are well aware of a variety of vacuum panel configurations. The vacuum panels tend to focus the change-in-shape allowing the container to retain a pleasing generally uniform appearance. Retaining the pleasing generally uniform appearance is an important consideration to the packager and its customers. If the container should collapse in an un-uniform manner, the container appearance becomes less pleasing and the customer becomes reluctant to purchase, believing the product damaged.
Packagers attempting to reduce cost, require containers to have less material or to be lighter in weight. Accordingly, containers lighter in weight are more vulnerable to unwanted changes-in-shape. FIG. 1 illustrates a typical container having a plurality of vacuum panels. The area (generally illustrated in FIG. 1 as a shaded circular spot) above and/or below any adjacent pair of vacuum panels is often vulnerable to unwanted collapse. FIG. 2 is a bottom view of the container shown in FIG. 1 illustrating its typical generally circular configuration.
Container and bottle designers further attempting to control unwanted changes-in-shape have added reinforcing grooves or ribs (not illustrated) at or near the shaded circular spots shown on FIG. 1. Those skilled in the art are aware of a number of variations. Unfortunately, as packagers continue to remove additional weight from the container, to further reduce cost, reinforcing grooves or ribs have been found to become inadequate.
Accordingly, the inventors have discovered a new and novel rib configuration which is more adequate for controlling unwanted changes-in-shape of the polymer container, in particular of the polyester polymer container.